Appliance for drying hands by means of hot air



March 12, 1968 H. LEDERMANN 3,372,490

' I APPLIANCE FOR DRYING HANDS BY MEANS OF HOT AIR Filed June 27, 1965 United States Patent Office 3,372,490 Patented Mar. 12, 1968 3,372,490 APPLIANCE FOR DRYING HANDS BY MEANS OF HOT AIR Hugo Ledermann, Eichstrasse, Ucrikon, Zurich, Switzerland Filed June 27, 1966, Ser. No. 560,749 3 Claims. (Cl. 34-76) ABSTRACT OF THE DISCLOSURE An appliance for drying hands by means of hot air in which an airflow for ultimate introduction into an outwardly open space for the hands is subjected to an initial dehumidification for reducing the water vapor pressure to less than that existing on the hands to be dried and thereafter heated and directed into the outwardly open space. The storage of the cold energy and heat energy permits the appliance to become directly effective without loss of time for the preliminary cooling or heating of the exchange surfaces in use.

The present invention has as its object an appliance for drying the hands, by means of hot air.

Appliances are employed for drying the hands and other parts of the body including the face and the scalp hair which are wet after washing, in which heated air is blown onto the areas to be dried. The appliances known for this purpose differ in the mode of air deflection, arrangement, and number and size of the hot air egress apertures. These appliances all have in common as a rule that the air-to be heated is drawn from the surrounding space and introduced directly over an electrical heating element. Although heating of the air increases its enthalpy, its content of water vapor remains unchanged. The drying action does not however depend solely on the difference in temperature between the hot air and the area to be dried, but equally on the difference in vapor pressure between the dampness adhering to the surface of the body and that of the vapor contained in the air. The greater the humidity of the air, the greater its vapor pressure, and heating of the air does not cause any change. The drying action represents a simultaneous twofold exchange, namely an exchange of energy and an energy of substance, with the latter due to the fact water vapor .passes into the air from the damp part of the body, and an exchange of energy in which heat is transferred from .the air to the surface of the body to vaporize the film of water adhering thereto.

The transfer of substance occurs only while the vapor pressure at the surface of the body is higher than that of the vapor contained in the air. The water vapor pressure at the surface of the body is established by its temperature and degree of humidity. In the case of hands, the temperature amounts to say 24 to 27 C., with the relative humidity lying within the range from 40 to 50% for dry hands, and from 50 to 70% for wet hands. As a mean value, the vapor pressure at the surface of a dry hand may be assumed as 1.5 millibar, and of a wet hand as 2.0 millibar.

However, the condition of the air in rooms containing hand driers varies very considerably. Temperatures of between "18 and. 22 C. and relative atmospheric humidities of 6 to 80% may be observed during the warm season. The mean value of vapor pressure amounts to approximately 1.7 millibars in this case, and is not changed by heating the air. Since the vapor pressure in the air exceeds the value of 1.5 millibars given for the surface of a dry hand, complete drying cannot be accomplished due to the absence of the difference in vapor pressure between the surface of the hand and the hot air necessary for transfer of substance. By prolonging the drying action, it is possible to increase the temperature of the surface of the hand, thus raising the vapor pressure of the film of water covering the same, so that an effective difference in vapor pressures is re-established. This entails a longer period and the application of greater power since heat is required not only for vaporizing the film of Water, but also for heating the surface of the hand. When the hands are withdrawn from the flow of hot air, their surface cools again, and is accompanied by an increase in relative humidity thereby resulting in a disagreeable feeling of dampness. The result of the drying action and the time to be spent on the same thus depend on the humidity content of the surrounding atmosphere.

It is an object of the invention to eliminate the cor responding shortcomings of known hot air driers by largely eliminating the influence of the different conditions of the surrounding atmosphere. The present invention is directed to a hot air drier for the hands which comprises a blower installed within a casing for the generation of a flow of air, means for heating the flow of air, an outwardly open treatment space situated within the casing or connected thereto, and a device for the preliminary dehumidification of the air drawn in to a lower vapor pressure than that on the surface of the hands to be dried, is in advance of the means for heating the flow of air.

Dehumidification of the air drawn in causes a drop in the vapor pressure of the water vapor contained in the flow of hot air. This dehumidification may be performed in manner known per se, by cooling the air drawn in prior to heating the same to the temperature desired for treatment, with the result of maintaining a difference in vapor pressure effective for transfer of substance throughout the drying action, without having to raise the temperature of the hands to be dried.

Further objects and advantages of the invention will become more readily apparent to persons skilled in the art from the following detailed description and annexed drawings in which the sole figure is a diagrammatic view of a hot air drier for hands embodying the invention and operating according to thermodynamic principles.

The hot air drier illustrated includes a casing 21 having an ingress opening 23 at approximately the middle of one side wall above a horizontal partition 22. A cold water container 24 provided with vertical cooling surfaces'25 is situated in the casing 21 above the ingress opening 23. The air entering through the ingress opening 23 is conducted by a guide plate 26 between the cooling surfaces 25 of the cold water container 24. A hot water container 27 provided with vertical heating surfaces 28 is situated in the casing 21 above the cold water container 24. The air issuing between the cooling surfaces 25 of the cold water container 24 passes between the heating surfaces 28 of the hot water container 27 and, after passing over surfaces 28 enters into the upper part of the casing 21 in a heated condition. An evaporator 29 in the form of a coiled tube is arranged in the container 24 and is connected at one side to an expansion device 31 and at the other to a compressor 30. A condenser 32 is arranged in the hot water container 27 and is connected at one side to the compressor 30 and at the other to the expansion device 31. The evaporator 29 and the condenser 32 are traversed by a coolant.

An electric motor 33 having a vertical spindle is located 'above the partition 22 and the spindle extends through a suction opening 34 in the partition 22. A fan or impeller 35 is secured to the spindle and draws air through the suction opening 34 from the upper part of the casing 21 and forces the same into a pressure space 36 situated below the partition 22 in the lower part of the casing 21. In the pressure space 36 is located an outwardly open treatment space 37 having spaced-apart air ingress openings 38 in its sides.

The hot air drier operates in the following manner:

Heat is supplied to the cold water container 24 by the flow of air and the heat causes evaporation of the coolant in the evaporator 29. The coolant vapor is compressed by the compressor 30 and forced into the condenser 32 in which it liquefies to give off heat. The water in the hot water container 27 is heated. The coolant is expanded in the expansion device and again vaporized in the evaporator 29 thus drawing heat from the water in the cold water container 24 and refrigerating the same until ice is formed. When the initial state desired is reached, the compressor 30 is deactivated for example by means of a pressure-operated switch. Since either water, that is to say at a temperature C., is present in the cold water container 24, the temperature of the cooling surfaces of the container 24 cannot drop below the freezing point, thus reliably preventing the formation of ice on the cooling surfaces 25.

When the electric motor is activated for a drying action, air is drawn in through the ingress opening 23, passes over the cooling surfaces 25 of the cold water container 2 4 and thereafter over the heating surfaces 28 of the hot water container 27. The air enters the upper part of the casing and is forced into the pressure space 36 by the impeller 35, and from which pressure space it flows into the treatment space through the ingress openings 38. The air entering the ingress opening 23 is cooled on the cooling surfaces 25 of the cold water container 24 with the greater proportion of the water vapor contained thereby being caused to condense on the cooling surfaces 25 in the form of water which is drained in any suitable manner. Heat is transferred to the water present in the cold water container 24 thereby melting a part of the ice contained therein. The air which is cooled and thus dehumidified, thereupon passes over the heating surfaces 28 of the hot water container 27 on which it is heated to the temperature required for treatment. Heat is thus drawn from the water in the hot water container 27. After a certain period of operation, the pressure of the coolant vapor in the evaporator 29 rises, and when an upper limit is reached, the compressor 30 is again activated. This causes renewed cooling of the water in the cold water container 24 under renewed ice formation, and renewed heating of the water in the hot water container 27.

The cooling system defined by the components 24-32 and the electric motor 33 carrying the impeller 35 are activated and deactivated independently with the first being operated according to the operating condition in existence, and the second by the actuation of a switch when a drying action is required. The period of operation of the electric motor 33 may be controlled chronologically in a mechanical, thermic or electronic manner known per se.

The storage capacity of the cold water container 24 in cooling units and of the hot water container 27 in calories, amounts to a multiple of the value required for one drying action. The cooling and heating performance respectively is determined by the capacity of the heat exchange surfaces, that is to say by the areas the cooling surfaces 25 and of the heating surfaces 28. By contrast, the cooling and heating performance respectively does not depend directly on the cooling and heating performance respectively of the cooling system defining components 24-32, as the latter is calculated from the sum of cooling and heating requirements for several drying actions over a longer period. The storage capacity of the cold water container 24 and the hot water container 27 may be such that ten drying actions following each other imediately limit the power demand to ten minutes, whereas it must be made up by the cooling system defining components 2432 in the course of one hour. The nominal rating of the cooling system defining components 24-32 may then be six times lower than would be necessary for a direct coverage of the power demand. The hot air drier may thus be made smaller and with lower power requirements, and its wattage is a fraction of that of a known hot air drier. Although the power demand is applied over a longer period, it is no higher in the final analysis.

The invention is not to be confined to any strict conformity to the showings in the drawings but changes or modifications may be made therein so long as such changes or modifications mark no material departure from the spirit and scope of the appended claims.

What I claim is:

1. An appliance for drying hands by hot air comprising a casing, means within the casing constituting an outwardly open space for the hands, means within the casing for creating an airflow within the casing for ultimate introduction into said outwardly open space, and means within the casing for preliminarily dehumidifying the air to reduce the water vapor pressure in the air to less than that existing on the hands to be dried and for heating such dehumidified air, said last named means including a cold water container having cooling surfaces and an evaporator therein, a hot water container following said cold water container and being in commuication therewith, said hot water container having heating surfaces and a condenser therein, and said evaporator and condenser being incorporated into a closed system traversed by a coolant by means of a compressor operably connected to one side of said evaporator and condenser and by an expansion device to the other side of said evaporator and condenser so that air entering said casing initially passes over the cooling surfaces of said cold water container and thereafter over the heating surfaces of said hot water container.

2. The appliance for drying hands as claimed in claim 1, in which said cold and hot water containers are of such dimensions as to provide a storage capacity sufficient for a plurality of drying operations.

3. The appliance for drying hands as claimed in claim 2 in which said casing is divided into upper and lower compartments by a horizontal partition, said means for creating an airflow and said means constituting an outwardly open space for the hands being located in said lower compartment, said cold and hot water containers, said compresser and said expansion device being in said upper compartment and said partition having an opening in communication with said means for creating an airflow.

References Cited UNITED STATES PATENTS 1,791,038 2/1931 Opavsky.

2,314,101 3/1943 Phipps 34-77 2,783,547 3/1957 Bieger et a1. 34-80 X 2,884,855 5/1959 Koch 3480 X 2,981,267 4/1961 Stoddard.

2,979,828 4/1961 Westeren 34-80 X 3,068,587 12/1962 Toellner 34-80 X 3,263,342 8/1966 Giuflre 3476 3,304,623 2/1967 Reiss et al. 3480 FREDERICK L. MATTESON, JR., Primary Examiner.

A. D. HERRMANN, Assistant Examiner. 

